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[SOLVED] Re: DVD... plus or minus?

 
 
Mike Tomlinson
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      Aug 30th, 09, 3:55 PM
In article <q1pmm.35130$2>, Chris Whelan
<> writes

>K3B (on Linux) somehow tests the drive for optimum burning speed, and
>will only allow that as a maximum unless the user over-rides the auto
>setting.


It actually reads it from the disk.

> )It's surprising how different this often is from the
>theoretical speed!) IME this works well; the same batch of disks in
>different drives will burn at different speeds.


Odd.

A good rule of thumb is to burn at half the rated speed of the disc
(e.g. 24x for 48x CDs, 4x for 8x DVDs). Someone on this group suggested
this tip a few years ago and it's stood me in good stead on several
different PCs and drives.

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(='.'=) Bunny says Windows 7 is Vi$ta reloaded.
(")_(") http://imgs.xkcd.com/comics/windows_7.png


 
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Johnny B Good
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      Aug 30th, 09, 10:28 PM
The message <>
from Mike Tomlinson <> contains these words:

> In article <q1pmm.35130$2>, Chris Whelan
> <> writes


> >K3B (on Linux) somehow tests the drive for optimum burning speed, and
> >will only allow that as a maximum unless the user over-rides the auto
> >setting.


> It actually reads it from the disk.


> > )It's surprising how different this often is from the
> >theoretical speed!) IME this works well; the same batch of disks in
> >different drives will burn at different speeds.


> Odd.


> A good rule of thumb is to burn at half the rated speed of the disc
> (e.g. 24x for 48x CDs, 4x for 8x DVDs). Someone on this group suggested
> this tip a few years ago and it's stood me in good stead on several
> different PCs and drives.


That's 'sound' advice when it comes to burning music CDs intended to be
playable on standard music CD players. However, a safer choice is to
pick a speed that's either no greater than the media's rating or no more
than about 40% of the drive's max writing speed whichever is the more
limiting.

This should allow the drive to employ a CLV [1] writing strategy which
avoids the laser power level switching required of the CAV [1] method
used to achieve maximum write speeds. The sudden changes of contrast at
each power level switching point can prove problematical for a lot of
music CD players.

As far as data formats go, such transitions in contrast are not a
problem with CD drives used in PCs. The issue doesn't exist in the DVD
formats since a DVD movie is simply a data DVD that happens to have
movie files in a standardised directory structure format.

Of course, you might elect to write at a slower speed than the max
simply to minimise the likelyhood of creating coasters, especially if
the media's speed rating seems over-optimistic with your particular
drive.

[1] CLV = Constant Linear Velocity. The disk spins at maximum rpm to
start with, gradually slowing down as the write operation proceeds to
its completion. This maintains a constant velocity along the single
spiral 'groove' allowing a constant bit stream rate and a constant level
of laser power.)

CAV = Constant Angular Velocity. The disk spins at its (or the drive's)
maximum rpm from start to finish requiring a steady increase in both
data rate and laser power as the linear scan velocity along the 'groove'
gets faster and faster as the head assembly moves further away from the
centre of the disk. Unfortunately, laser power cannot be smoothly varied
to match the data rate, merely approximated to a smooth variation in a
succession of discrete steps.

--
Regards, John.

Please remove the "ohggcyht" before replying.
The address has been munged to reject Spam-bots.

 
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